Polybenzimidazoles (PBI) are among the most thermally stable polymers known.1-5 As well as high temperature stability, the polymers have excellent flammability resistance and high chemical resistance. They are very expensive polymers but have found uses as a high performance fiber and as a film, foam, paper and in membranes for polymer electrolyte membrane fuel cells. The most common structure is synthesized by reaction of biphenyl-3,3′,4,4′-tetraamine with isophthalic acid and these conversions have been carried out under a wide variety of conditions.4

Poly (N-phenylbenzimidazoles)6-8 have also been synthesized. They are more soluble and are reported to be more thermooxidatively stable than the parent PBI polymers since the NH group has been replaced by a phenyl group.

Several years ago, the present inventors found that high molecular weight polymers could be prepared from 4-(4-hydroxyphenyl)phthalazin-1(2H)-one by reaction with activated halides.9,10 The N—C coupling reaction was unexpected since the NH group behaves like a phenolic OH group in this reaction. These polymers are excellent high temperature thermoplastics and are currently being commercialized in China.

The present inventors subsequently prepared bisphthalazinone structures from the monomers shown in Scheme 111, however, these polymers were very difficult to process because of crystallinity and very high glass transition temperatures. This problem was recently alleviated by the synthesis of the more flexible monomers shown in Scheme 2.12,13


There has been a great deal of recent effort centered on Pd-catalyzed C—N coupling reactions of NH groups with unactivated halides,26,27 as well as methods to improve the standard Ullmann-type, copper-catalyzed, reactions.28,29 These reactions generally require the use of aryl bromides or iodides and quite high yields have been obtained. These reactions have not been reported for the formation of high molecular weight polymers.
In a series of papers and patents, Hergenrother and associates described the synthesis of high performance polymers, poly(aryl ether)benzimidazoles, by the reaction of bisphenols containing benzimidazole moieties with activated halides.14-17 The synthesis, properties and potential applications of this class of polymers has been extensively reviewed.18

Connell found that isophthaloyl-containing poly(aryleneether benzimidazoles (PAFBI) exhibited high mechanical properties in the form of unoriented thin films and carbon fiber reinforced composites.22 
Poly (arylene ether)s containing N-arylenebenzimidazole groups were also prepared by the aromatic nucleophilic displacement reaction of two new bis(hydroxyphenyl-N-arylenebenzimidazole)s with activated aromatic difluorides in sulfolane at 200° C. in the presence of anhydrous potassium carbonate.14,15,19-24 The polymers exhibited glass transition temperatures ranging from 264 to 352° C. and inherent viscosities from 0.79 to 1.99 dl g−1 and had very good thermal stability.5,14

The polymers exhibited lower Tgs, tensile properties, and moisture uptake than poly(arylene ether benzimidazole)s, presumably due to the lack of hydrogen bonding. The preparation of these polymers, as illustrated in the example immediately below, is a very lengthy and expensive process and some of the intermediates are carcinogenic.8

It is an object of this invention to provide novel polymers and copolymers.
It is another object of this invention to provide methods for the manufacture of the novel polymers and copolymers.
Novel polymers and copolymers of this invention have value resulting from their thermal stability and their ability to form films, including flexible films, by casting from solution, which films may be employed in a variety of applications, including high performance applications, for example as electrolyte membranes in fuel cells. In particular the excellent high temperature properties of the polymers and copolymers make them useful as films, matrices in carbon fiber reinforced composites and high performance adhesives.
A first aspect of the invention relates to novel polymers and copolymers thereof. The novel polymers are of the formula I
wherein Ar, Ar2, Ar3, and X are defined as follows:
Ar is a divalent radical selected from the group consisting of:

Ar2 is a fused ring selected from the group consisting of:

Ar3 is a divalent radical selected from the group consisting of:

X is a divalent radical selected from the group consisting of:
and (m+n) ranges from 1 to 10,000, preferably 1 to 1000, and more preferably 30 to 500, where m is an integer of at least 1, and preferably 30 to 500, and n is an integer from 0 to 9999, preferably 0 to 999, and more preferably 0 to 500.
In another aspect of the invention there is provide a process for preparing the novel polymers and copolymers by a novel carbon-nitrogen (C—N) coupling of benzimidazoles to activated halides at temperatures not below 160° C., ie a temperature of at least 160° C. The polymers are prepared by
a process which comprises the reaction step at a temperature of no less than 160° C., ie. a temperature of at least 160° C., wherein Ar, Ar2, X, m and n are as defined above, and Halogen is selected from F, Cl, Br and I, preferably F or Cl.
The copolymers are prepared by a process which comprises the reaction step
at a temperature of no less than 160° C., ie. a temperature of at least 160° C., wherein Ar, Ar2, Ar3, X, m and n are as defined above, and Halogen is selected from F, Cl, Br and I, preferably F or Cl.